The luxurious, custom-built 24,000-square-foot home boasts six bedrooms, nine bathrooms, a massive in-ground pool, a wine cellar, an elevator, a game room -- and sits on its own 830,000 square-foot private island.

Why are Quebec native Dion, 44, and Angelil, 70 -- who have three children together, Rene-Charles, 11, and twins Eddy and Nelson, 19 months -- parting with their custom-made dream home?

"The house is being sold because of an intensive performance schedule over the next few years," reps for the couple tell Sotheby's. "The property is currently under-utilized so the family is looking at downsizing into a smaller home." (Dion is currently in the midst of a three-year residency at Caesars Palace in Las Vegas).

Adds the rep, "Ms. Dion's roots and family are here in Quebec, and as such, she will maintain a residence here."